The present invention relates generally to particulate composites made by laser ablative deposition. More particularly, the invention relates to a particulate composite alloy made by a single step laser ablative deposition method.
It is known that a laser can deliver an extremely high level of energy to a small surface area and to a volume of a material beneath the small surface area. The delivery of such high levels of energy causes the removal of a volume of material from the affected surface in the form of a plume of vaporized and ablated material and by a process which is described as ablative or ablation. The plume may also include radicals, ions, electronically excited species, electrons, photons, liquid droplets, microscopic as well as macroscopic particles in a variety of concentrations.
I have found that when a candidate metal is ablated and the material of the plume deposits on a surface, it may be made to form a metallic film which includes particles within a matrix of metal and other condensate. I have also found that for most materials the density and size of particles generated in the laser ablation process increases with increasing laser fluence. The various mechanisms by which the different constituents of a plume agglomerate or condense to form the film is not fully understood. Also, there is not a high degree of predictability as to precisely the form of film which will result when the ablation process is applied to a designated material. For some applications, the presence of particles in a deposited film can be deemed detrimental. For example, in efforts to form high temperature superconductors, the presence of particles is generally deemed to be adverse to the quality of the film for this purpose. For other applications, the presence of particulate matter may be deemed desirable. One problem in operating the ablation process is to increase the control over the mix of ablation products formed from the process. I have found that it is possible to form a particulate composite, that is, a composite in which particles are deposited within a matrix of a host metal, by a single step ablative processing.